Zonal and Eddy Components of the Synoptic-Scale Energy Budget during Intensification of Hurricane Carmen (1974)

Frederick E. Brennan Department of Geosciences, Purdue University, West Lafayette IN 47907

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Dayton G. Vincent Department of Geosciences, Purdue University, West Lafayette IN 47907

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Abstract

A diagnostic analysis is presented of the partitioned kinetic and available potential energy budgets of the synoptic-scale circulation that occurs in conjunction with Hurricane Carmen (1974) during its intensification in the Caribbean from a tropical depression to a major hurricane. The zonal and eddy energy equations developed by Muench (1965) for the Northern Hemisphere stratosphere are derived in a more general form so that they can be applied to an area of limited latitudinal and longitudinal extent. Standard level rawinsonde and surface data are subjectively analyzed over the Caribbean area and grid-point values are extracted at increments of 2.5° latitude and longitude at 11 levels for eight consecutive synoptic times, 12 h apart, beginning 0000 GMT 30 August. To complete the energy budgets, vertical motion, momentum and heat transports and most of the diabatic heating terms are computed; however, frictional effects are neglected.

Results are composited into Carmen's.pre-hurricane and hurricane stages and show that many of the vortex-scale features known to be associated with an intense tropical system are resolved by the synoptic scale analysis. However, certain smaller scale features, such as the hurricane' central pressure, eye, eyewall and spiral rainbands, are not resolved. Results show that major changes take place in the synoptic-scale flow features as Carmen intensifies. Generation of both zonal and eddy available potential energy show large increases between Carmen's pre-hurricane and hurricane stages, due primarily to warming of the middle troposphere in response to convective heating processes. Correspondingly, thermally driven circulations in Carmen' vicinity are enhanced as evidenced by increases in conversions from zonal and eddy available potential energy to their respective kinetic energies. Furthermore, each form of kinetic energy is decreasing during Carmen's hurricane stage even though the storm's central pressure is falling rapidly; therefore, it is suggested that both the zonal and eddy components of the synoptic-scale flow are acting as sources of energy for the unresolvable features of Carmen' circulation.

Abstract

A diagnostic analysis is presented of the partitioned kinetic and available potential energy budgets of the synoptic-scale circulation that occurs in conjunction with Hurricane Carmen (1974) during its intensification in the Caribbean from a tropical depression to a major hurricane. The zonal and eddy energy equations developed by Muench (1965) for the Northern Hemisphere stratosphere are derived in a more general form so that they can be applied to an area of limited latitudinal and longitudinal extent. Standard level rawinsonde and surface data are subjectively analyzed over the Caribbean area and grid-point values are extracted at increments of 2.5° latitude and longitude at 11 levels for eight consecutive synoptic times, 12 h apart, beginning 0000 GMT 30 August. To complete the energy budgets, vertical motion, momentum and heat transports and most of the diabatic heating terms are computed; however, frictional effects are neglected.

Results are composited into Carmen's.pre-hurricane and hurricane stages and show that many of the vortex-scale features known to be associated with an intense tropical system are resolved by the synoptic scale analysis. However, certain smaller scale features, such as the hurricane' central pressure, eye, eyewall and spiral rainbands, are not resolved. Results show that major changes take place in the synoptic-scale flow features as Carmen intensifies. Generation of both zonal and eddy available potential energy show large increases between Carmen's pre-hurricane and hurricane stages, due primarily to warming of the middle troposphere in response to convective heating processes. Correspondingly, thermally driven circulations in Carmen' vicinity are enhanced as evidenced by increases in conversions from zonal and eddy available potential energy to their respective kinetic energies. Furthermore, each form of kinetic energy is decreasing during Carmen's hurricane stage even though the storm's central pressure is falling rapidly; therefore, it is suggested that both the zonal and eddy components of the synoptic-scale flow are acting as sources of energy for the unresolvable features of Carmen' circulation.

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